Sync tool for music or libraries

I have 3 PC 2 i use and 1 my brother uses and we want to have the same music on all our PC's and i have tried many syncing tool and although they work and sync across the network just fine, it always ends up messing up the library.

With the sync apps i tried any changes of new files or changes to files are re created on the other side and this is the problem. If i have 10 new songs it will copy the 10 songs across the network just fine, but if 50 songs have changed from a media update (album art, id3 tag's etc) or whatever from WMP it copies it across the network.

When you open wmp on a PC you see the 10 new songs and 50 old songs all added on the same date and this gets confusing if you have 2000+ files to find new music. The sync program i was using just recently did a library scan over the network and it updated all my files and in WMP every single song that was added 2 years ago is readded and says it was added july 17 2010 and now i know no way of knowing what is new or what is old in WMP.

I can check the date modified in explorer to know what file is new but is there a way to get date modified as a field in WMP, i use the date added feild in WMP to know what songs are new and what are old but it dose not work to well if your entire library gets refreshed.

Mainly i'm looking for a application that will only copy new files that are added to the music folder and ignore all old files even the ones that have updated. I just want a app that transfersnew files, since wmp always updates the mp3 file finding album art and what not i don't need that and i don't need updated files being copied across the network just new files that are added and nothing more.